Depolarization, in biology, refers to a sudden change within a cell, during which the cell undergoes a dramatic electrical change. Most cells, especially those that compose the tissues of highly organized animals, typically maintain an internal environment that is negatively charged compared to the cell's surrounding environment. This difference in charge is called the cell's membrane potential. In the process of depolarization, the negative internal charge of the cell becomes positive for a very brief time. This shift from a negative to a positive internal cellular environment allows for the transmission of electrical impulses both within a cell and, in certain instances, between cells. This communicative function of depolarization is essential to the function of many cells, communication between cells, and the overall function of an organism.